Source code for openquake.hazardlib.source.simple_fault

# The Hazard Library
# Copyright (C) 2012-2014, GEM Foundation
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
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"""
Module :mod:`openquake.hazardlib.source.simple_fault` defines
:class:`SimpleFaultSource`.
"""
import math
import numpy
from openquake.hazardlib.source.base import ParametricSeismicSource
from openquake.hazardlib.geo.surface.simple_fault import SimpleFaultSurface
from openquake.hazardlib.geo.nodalplane import NodalPlane
from openquake.hazardlib.source.rupture import ParametricProbabilisticRupture
from openquake.hazardlib.slots import with_slots


@with_slots
[docs]class SimpleFaultSource(ParametricSeismicSource): """ Simple fault source typology represents seismicity occurring on a fault surface with simple geometry. :param upper_seismogenic_depth: Minimum depth an earthquake rupture can reach, in km. :param lower_seismogenic_depth: Maximum depth an earthquake rupture can reach, in km. :param fault_trace: A :class:`~openquake.hazardlib.geo.line.Line` representing the line of intersection between the fault plane and the Earth's surface. :param dip: Angle between earth surface and fault plane in decimal degrees. :param rake: Angle describing rupture propagation direction in decimal degrees. :param hypo_loc: Array describing the relative position of the hypocentre on the rupture surface. Each line represents an hypocentral position defined in terms of the relative distance along strike and dip (from the upper, left corner of the fault surface i.e. the corner which results from the projection at depth of the first vertex of the fault trace) and the corresponding weight. Example 1: one single hypocentral position at the center of the rupture will be described by the following array[(0.5, 0.5, 1.0)]. Example 2: two possible hypocenters are admitted for a rupture. One hypocentre is located along the strike at 1/4 of the fault length and at 1/4 of the fault width along the dip and occurs with a weight of 0.3, the other one is at 3/4 of fault length along strike and at 3/4 of fault width along strike with a weight of 0.7. The numpy array would be entered as numpy.array([0.25, 0.25, 0.3], [0.75, 0.75, 0.7]). See also :class:`openquake.hazardlib.source.base.ParametricSeismicSource` for description of other parameters. :raises ValueError: If :meth:`~openquake.hazardlib.geo.surface.simple_fault.SimpleFaultSurface.check_fault_data` fails, if rake value is invalid and if rupture mesh spacing is too high for the lowest magnitude value. """ __slots__ = ParametricSeismicSource.__slots__ + '''upper_seismogenic_depth lower_seismogenic_depth fault_trace dip rake hypo_list'''.split() def __init__(self, source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing, magnitude_scaling_relationship, rupture_aspect_ratio, temporal_occurrence_model, # simple fault specific parameters upper_seismogenic_depth, lower_seismogenic_depth, fault_trace, dip, rake, hypo_list=numpy.array(None)): super(SimpleFaultSource, self).__init__( source_id, name, tectonic_region_type, mfd, rupture_mesh_spacing, magnitude_scaling_relationship, rupture_aspect_ratio, temporal_occurrence_model ) NodalPlane.check_rake(rake) SimpleFaultSurface.check_fault_data( fault_trace, upper_seismogenic_depth, lower_seismogenic_depth, dip, rupture_mesh_spacing ) self.fault_trace = fault_trace self.upper_seismogenic_depth = upper_seismogenic_depth self.lower_seismogenic_depth = lower_seismogenic_depth self.dip = dip self.rake = rake min_mag, max_mag = self.mfd.get_min_max_mag() cols_rows = self._get_rupture_dimensions(float('inf'), float('inf'), min_mag) self.hypo_list = hypo_list if 1 in cols_rows: raise ValueError('mesh spacing %s is too high to represent ' 'ruptures of magnitude %s' % (rupture_mesh_spacing, min_mag))
[docs] def get_rupture_enclosing_polygon(self, dilation=0): """ Uses :meth:`openquake.hazardlib.geo.surface.simple_fault.SimpleFaultSurface.surface_projection_from_fault_data` for getting the fault's surface projection and then calls its :meth:`~openquake.hazardlib.geo.polygon.Polygon.dilate` method passing in ``dilation`` parameter. See :meth:`superclass method <openquake.hazardlib.source.base.BaseSeismicSource.get_rupture_enclosing_polygon>` for parameter and return value definition. """ polygon = SimpleFaultSurface.surface_projection_from_fault_data( self.fault_trace, self.upper_seismogenic_depth, self.lower_seismogenic_depth, self.dip ) if dilation: return polygon.dilate(dilation) else: return polygon
[docs] def iter_ruptures(self): """ See :meth: `openquake.hazardlib.source.base.BaseSeismicSource.iter_ruptures`. Generates a ruptures using the "floating" algorithm: for all the magnitude values of assigned MFD calculates the rupture size with respect to MSR and aspect ratio and then places ruptures of that size on the surface of the whole fault source. The occurrence rate of each of those ruptures is the magnitude occurrence rate divided by the number of ruptures that can be placed in a fault. """ whole_fault_surface = SimpleFaultSurface.from_fault_data( self.fault_trace, self.upper_seismogenic_depth, self.lower_seismogenic_depth, self.dip, self.rupture_mesh_spacing ) whole_fault_mesh = whole_fault_surface.get_mesh() mesh_rows, mesh_cols = whole_fault_mesh.shape fault_length = float((mesh_cols - 1) * self.rupture_mesh_spacing) fault_width = float((mesh_rows - 1) * self.rupture_mesh_spacing) for (mag, mag_occ_rate) in self.get_annual_occurrence_rates(): rup_cols, rup_rows = self._get_rupture_dimensions( fault_length, fault_width, mag ) num_rup_along_length = mesh_cols - rup_cols + 1 num_rup_along_width = mesh_rows - rup_rows + 1 num_rup = num_rup_along_length * num_rup_along_width occurrence_rate = mag_occ_rate / float(num_rup) for first_row in xrange(num_rup_along_width): for first_col in xrange(num_rup_along_length): mesh = whole_fault_mesh[first_row: first_row + rup_rows, first_col: first_col + rup_cols] if self.hypo_list.size == 1: hypocenter = mesh.get_middle_point() occurrence_rate_hypo = occurrence_rate surface = SimpleFaultSurface(mesh) yield ParametricProbabilisticRupture( mag, self.rake, self.tectonic_region_type, hypocenter, surface, type(self), occurrence_rate_hypo, self.temporal_occurrence_model ) else: for hypo in self.hypo_list: surface = SimpleFaultSurface(mesh) hypocenter = surface.get_hypo_location( mesh, self.rupture_mesh_spacing, hypo[:2]) occurrence_rate_hypo = occurrence_rate * \ hypo[2] yield ParametricProbabilisticRupture( mag, self.rake, self.tectonic_region_type, hypocenter, surface, type(self), occurrence_rate_hypo, self.temporal_occurrence_model )
[docs] def count_ruptures(self): """ See :meth: `openquake.hazardlib.source.base.BaseSeismicSource.count_ruptures`. """ whole_fault_surface = SimpleFaultSurface.from_fault_data( self.fault_trace, self.upper_seismogenic_depth, self.lower_seismogenic_depth, self.dip, self.rupture_mesh_spacing ) whole_fault_mesh = whole_fault_surface.get_mesh() mesh_rows, mesh_cols = whole_fault_mesh.shape fault_length = float((mesh_cols - 1) * self.rupture_mesh_spacing) fault_width = float((mesh_rows - 1) * self.rupture_mesh_spacing) counts = 0 for (mag, mag_occ_rate) in self.get_annual_occurrence_rates(): rup_cols, rup_rows = self._get_rupture_dimensions( fault_length, fault_width, mag ) num_rup_along_length = mesh_cols - rup_cols + 1 num_rup_along_width = mesh_rows - rup_rows + 1 counts += num_rup_along_length * num_rup_along_width return counts
def _get_rupture_dimensions(self, fault_length, fault_width, mag): """ Calculate rupture dimensions for a given magnitude. :param fault_length: The length of the fault as a sum of all segments, in km. :param fault_width: The width of the fault, in km. :param mag: Magnitude value to calculate rupture geometry for. :returns: A tuple of two integer items, representing rupture's dimensions: number of mesh points along length and along width respectively. The rupture is reshaped (conserving area, if possible) if one of dimensions exceeds fault geometry. If both do, the rupture is considered to cover the whole fault. """ area = self.magnitude_scaling_relationship.get_median_area( mag, self.rake ) rup_length = math.sqrt(area * self.rupture_aspect_ratio) rup_width = area / rup_length # clip rupture's length and width to fault's length and width # if there is no way to fit the rupture otherwise if area >= fault_length * fault_width: rup_length = fault_length rup_width = fault_width # reshape rupture (conserving area) if its length or width # exceeds fault's length or width elif rup_width > fault_width: rup_length = rup_length * (rup_width / fault_width) rup_width = fault_width elif rup_length > fault_length: rup_width = rup_width * (rup_length / fault_length) rup_length = fault_length # round rupture dimensions with respect to mesh_spacing # and compute number of points in the rupture along length # and width (aka strike and dip) rup_cols = int(round(rup_length / self.rupture_mesh_spacing) + 1) rup_rows = int(round(rup_width / self.rupture_mesh_spacing) + 1) return rup_cols, rup_rows